Paramagnetic Resonance of Transition Elements and Irradiated Substances

Unpaired s -electrons play an important part in hyperfine spectra, even when the nominal spectroscopic configuration contains no unpaired s -electrons. This situation occurs in paramagnetic resonance and optical spectra. A survey of the experimental evidence for the effect is given in relation to the paramagnetic ions and the neutral atoms of the 3 d transition elements. It appears that the central density of unpaired spin is nearly the same in all the ions of the group for which experimental data are available, while for the neutral atoms it is more variable, but of the same general magnitude. A calculation of the magnitude of the effect is attempted from first principles, starting from the Hartree–Fock self-consistent wave functions as a first approximation, and adding configurations in which 3 s -, 2 s - and 1 s -electrons are promoted. The promotion of a 3 s -electron is described by an integro-differential equation, which has been solved numerically in one particular case. The contribution turns out of the right sign but ten times smaller than the observed value. Promotion of 2 s - and l s -electrons yield similar equations, which, however, have not been solved, owing to the excessive labour involved. There is no reason to believe that they would not give smaller contributions still. The full explanation of the s -electron effect is thus still an open question.

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On the magnetic properties of covalent XY 6 complexes

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1953.0166 ◽

1953 ◽

Vol 219 (1139) ◽

pp. 542-555 ◽

Cited By ~ 313

Keyword(s):

Magnetic Properties ◽

Hyperfine Structure ◽

Molecular Orbitals ◽

Transition Elements ◽

Paramagnetic Resonance ◽

Magnetic Carriers

An account is given of present ideas about the electron orbits in octahedral complexes containing 4 d and 5 d transition elements, with particular reference to paramagnetic resonance. The complex is treated by the method of molecular orbitals with the assumption that the magnetic carriers are partly in central d -orbits and partly in p π -orbits round the outer nuclei. This is shown to lead to a reduction in the orbital g -factor and to the possibility of observing the hyperfine structure from the outer nuclei, thus testing the initial assumptions.

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Study of charge transfer in FeTi

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075270 ◽

1983 ◽

Vol 41 ◽

pp. 296-297

Author(s):

J. Taft∅

Keyword(s):

Charge Transfer ◽

Charge Distribution ◽

Electron Scattering ◽

Periodic System ◽

Electron Distribution ◽

Scattering Amplitude ◽

Transition Elements ◽

Hartree Fock ◽

Cscl Structure ◽

The Right

It is well known that for reflections corresponding to large interplanar spacings (i.e., sin θ/λ small), the electron scattering amplitude, f, is sensitive to the ionicity and to the charge distribution around the atoms. We have used this in order to obtain information about the charge distribution in FeTi, which is a candidate for storage of hydrogen. Our goal is to study the changes in electron distribution in the presence of hydrogen, and also the ionicity of hydrogen in metals, but so far our study has been limited to pure FeTi. FeTi has the CsCl structure and thus Fe and Ti scatter with a phase difference of π into the 100-ref lections. Because Fe (Z = 26) is higher in the periodic system than Ti (Z = 22), an immediate “guess” would be that Fe has a larger scattering amplitude than Ti. However, relativistic Hartree-Fock calculations show that the opposite is the case for the 100-reflection. An explanation for this may be sought in the stronger localization of the d-electrons of the first row transition elements when moving to the right in the periodic table. The tabulated difference between fTi (100) and ffe (100) is small, however, and based on the values of the scattering amplitude for isolated atoms, the kinematical intensity of the 100-reflection is only 5.10-4 of the intensity of the 200-reflection.

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